Vice News reports that in January, Colombia saw an unusual increase in cases of Guillain-Barre Syndrome, a rare disorder where a person’s immune system attacks the nervous system, in some cases temporarily paralyzing the body and requiring hospitalization.

As in neighboring Brazil and Venezuela, the uptick in Colombia happened at the same time as a local Zika outbreak, leading experts to begin searching for a connection. Researchers have since rushed to find out more, and a new report published Wednesday in the New England Journal of Medicine outlines the most compelling evidence to date linking the mosquito-borne virus to the debilitating disorder.

The study analyzed 68 patients with Guillain-Barre syndrome this year at six Colombian hospitals. Researchers determined the presence of Zika infection in those patients offered enough evidence to support the idea that the virus sparks the onset of the syndrome.

“The fact that we found Zika infection in those patients is good evidence that Zika may contribute to development of the disease,” said Beatriz Parra, one of the study’s authors and a researcher at Universidad del Valle in Colombia. As she explained, the evidence strongly supports a link between Zika and Guillain-Barre syndrome.